Power operated dermatome with rotary knife blade

ABSTRACT

A head assembly ( 200 ) for a power operated dermatome ( 100 ) including a frame body or housing ( 202 ) supporting a gear train ( 520 ), a blade housing assembly ( 400 ), an annular rotary knife blade ( 300 ) supported for rotation about an axis of rotation (R) by the blade housing assembly ( 400 ). The rotary knife blade ( 300 ) includes an inner wall ( 365 ) defining an interior region ( 301 ) and has a cutting edge ( 360 ) at one end ( 368 ) defining a cutting plane (CP). The head assembly ( 200 ) further includes a depth gauge assembly ( 600 ) including a depth gauge support ( 602 ) and a depth gauge ( 620 ) including a depth gauge plate ( 622 ) supported by the depth gauge support ( 602 ) for axial movement along the axis of rotation (R), the depth gauge plate ( 622 ) extending into the interior region ( 301 ) and the depth gauge support ( 602 ) attached to and extending from the frame body ( 202 ).

TECHNICAL FIELD

The present disclosure relates to a power operated dermatome including arotary knife blade and depth gauge extending to an interior region ofthe rotary knife blade for removal of skin tissue for skin grafting andother medical purposes.

BACKGROUND

Dermatomes are hand-held surgical instruments used by a physician ormedical professional (hereinafter operator) for cutting thin layers orsections of skin tissue. Dermatomes are used in hospitals and othermedical facilities for excising or removal of skin tissue from patientsin connection with various medical procedures including split-thicknessand full-thickness skin grafting, skin debriding (e.g., removal ofburned skin tissue), tumor/lesion removal, and breast reduction, amongother procedures. Dermatomes are also used in to remove skin tissue fromdeceased human or animal donors for skin grafting purposes.

Prior dermatomes included both manual operated and power operateddermatomes. Manual dermatomes typically included a fixed blade and ahandle projecting from the blade. Manual dermatomes were often foundtedious to use and prone to operator fatigue, especially when largesections of skin tissue needed to be removed, requiring multiplesections of skin tissue to be removed. For example, a deceased humandonor may provide from 6-9 square feet of recoverable skin tissue.

It is generally desired that an excised skin section be of uniform orconsistent thickness along the longitudinal extent of the skin sectionand across the width of the skin section. The thickness of an excisedskin section is dependent on the depth of cut of the dermatome cuttingblade. Use of manual dermatomes often resulted in excised skin sectionsof varying thickness and having irregular edges. The uniformity of thedepth of cut was largely dependent on the skill of the operator. Whilelimited numbers of manual dermatomes continue to be used, power operateddermatomes are favored in procedures where large sections of skin tissueneed to be removed in an efficient manner and/or operator fatigue is anissue.

Prior power operated dermatomes typically included a reciprocatingcutting blade disposed at a front or leading edge of the dermatome witha guard or depth gauge to allow the operator to set a depth of cut ofthe dermatome to remove a desired thickness of skin tissue. The bladewas typically disposed orthogonally to a rearward extending handle orhand piece of the dermatome. Because the cutting direction of the bladeof prior power operated dermatomes was forward facing, such dermatomeconfigurations required the operator to move the dermatome in adirection generally away from the operator's body to excise or cut asection of skin tissue. This direction of movement of the operator'shand and the dermatome away from the operator's body is less natural andless precise that a direction of movement of the operator's hand anddermatome toward the operator. Moreover, in moving the dermatome awayfrom the operator's body, the position of the dermatome tends to blockthe area of the skin tissue being excised from the view of the operator.This is especially problematic where the tissue to be removed isadjacent to, for example, a raised or bony prominence of the body thatmust be carefully navigated around with the cutting edge of thedermatome cutting blade.

Additionally, with prior power operated dermatomes, in order to cut askin tissue section with a desired, consistent depth of cut, the angleof cut, the speed of the dermatome along the skin, and the pressureapplied to the dermatome had to be carefully controlled by the operator.The angle of cut of the dermatome refers to an acute angle between thedermatome cutting blade and the skin tissue being removed or excised. Ifthe angle of cut of the dermatome is too shallow, the desired depth ofcut will not be achieved. If the angle of cut of the dermatome is toosteep, gouging or trenching of the excised skin tissue will occur.Further, if the angle of cut is changed as the power operated dermatomeis moved along the skin tissue, the depth of cut will vary along alongitudinal extent of the excised section of skin tissue.

The speed or rate of forward movement of prior power operated dermatomesalso had to be carefully controlled by the operator. If the speed of thedermatome was too fast or too slow, the depth of cut of the excised skinsection may be greater or less than the desired depth of cut as set bythe operator using the dermatome depth gauge.

The operator using a typical prior power operated dermatome also wasrequired to apply considerable pressure to the dermatome to insure thatthe entire extent or length of the cutting edge of the reciprocatingblade remained in contact with the skin tissue. The pressure applied bythe operator to the dermatome needed to remain constant. If the pressureapplied by the operator to the dermatome was too high or too low duringa cutting operation, the depth of cut could change and the excised skinsection would have portions that were of greater or less depth than thedesired depth of cut as set with the dermatome depth gauge. If thepressure applied by the operator to the dermatome was too low, theexcised skin tissue may be too thin resulting in holes in the excisedskin tissue and/or chattered edges.

Uniformity in the depth of cut of excised skin sections is especiallyimportant in split thickness skin grafts where it desired to remove onlythe outer epidermis and a portion of the dermis. Desired skin tissuethickness in a thin-type split-thickness skin graft is on the order of0.127 to 0.304 mm. Thus, there is little margin for error where thedesired skin thickness and depth of cut is very thin.

With prior dermatomes using a reciprocating blade, it was sometimesnecessary for the operator to have an assistant provide counter-tractionto flatten the skin surface in front of or behind the path of travel ofthe dermatome to allow the dermatome blade to make an initial cut.Adding an additional person to the procedure not only increases the costof the procedure, but also increases the risk of infection andcontamination due to the presence of another person in the operating orprocedure room.

What is needed is a power operated dermatome wherein obtaining adesired, consistent thickness of an excised skin tissue section is lessdependent on operator skill in maintaining a constant, desired angle ofcut, speed and pressure on the dermatome. What is needed is a poweroperated dermatome that reduces operator fatigue when removing largesections of skin tissue. What is needed is a power operated dermatomethat facilitates the removal of skin tissue in tight spaces and aroundboney prominences. What is needed is a power operated dermatome thatfacilitates improved control of the dermatome by the operator by movingthe blade cutting edge along a path toward the operator, instead ofmoving the blade away from the operator. What is needed is a poweroperated dermatome that allows for improved visibility of the skin sitebeing excised by the operator. What is needed is a power operateddermatome that facilitates removal of very thin layers of skin tissueand tangential excision of burn tissue. What is needed is a poweroperated dermatome that does not require an additional person involvedin the procedure to provide counter-traction at the skin removal site topermit an initial cut to be made by the dermatome.

SUMMARY

In one aspect, the present disclosure relates to a head assembly for apower operated dermatome, the head assembly comprising: a frame bodysupporting a gear train, a blade housing assembly, an annular rotaryknife blade supported for rotation about an axis of rotation by theblade housing assembly, the rotary knife blade including an inner walldefining an interior region of the rotary knife blade and having acutting edge at one end of the rotary knife blade defining a cuttingplane orthogonal to the axis of rotation of the rotary knife blade, anda depth gauge assembly including a depth gauge support and a depth gaugeincluding a depth gauge plate supported by the depth gauge for axialmovement along the axis of rotation of the rotary knife blade, the depthgauge plate extending into the interior region of the rotary knife bladeand the depth gauge support attached to and extending from the framebody.

In another aspect, the present disclosure relates to a power operateddermatome comprising: an elongated handle assembly and a head assemblyremovably coupled to the handle assembly, the head assembly including aframe body supporting a gear train, a blade housing assembly, an annularrotary knife blade supported for rotation about an axis of rotation bythe blade housing assembly, the rotary knife blade including an innerwall defining an interior region of the rotary knife blade and having acutting edge at one end of the rotary knife blade defining a cuttingplane orthogonal to the axis of rotation of the rotary knife blade, anda depth gauge assembly including a depth gauge support and a depth gaugeincluding a depth gauge plate supported by the depth gauge for axialmovement along the axis of rotation of the rotary knife blade, the depthgauge plate extending into the interior region of the rotary knife bladeand the depth gauge support attached to and extending from the framehousing.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and advantages of the presentdisclosure will become apparent to one skilled in the art to which thepresent disclosure relates upon consideration of the followingdescription of the invention with reference to the accompanyingdrawings, wherein like reference numerals, unless otherwise describedrefer to like parts throughout the drawings and in which:

FIG. 1 is a schematic perspective view of a first exemplary embodimentof a hand held, power operated dermatome of the present disclosureincluding a handle assembly and a head assembly including a rotary knifeblade and a depth gauge assembly extending into a central, interiorregion defined by the rotary knife blade;

FIG. 2 is a schematic exploded perspective view of the power operateddermatome of FIG. 1;

FIG. 3 is a schematic side elevation view of the power operateddermatome of FIG. 1;

FIG. 4 is a schematic top plan view of the power operated dermatome ofFIG. 1;

FIG. 5 is a schematic bottom plan view of the power operated dermatomeof FIG. 1;

FIG. 6 is a schematic front elevation view of the power operateddermatome of FIG. 1;

FIG. 7 is a schematic longitudinal section view of the power operateddermatome of FIG. 1, as viewed along a longitudinal axis LA of thehandle assembly of the dermatome;

FIG. 8 is a schematic top plan view of the head assembly of the poweroperated dermatome of FIG. 1, with a gear train of the head assemblyremoved for clarity;

FIG. 9 is a schematic rear elevation view of the head assembly of FIG.8;

FIG. 10 is a schematic exploded top perspective view of the headassembly of FIG. 8;

FIG. 11 is a schematic exploded bottom perspective view of the headassembly of FIG. 8;

FIG. 12 is a schematic section view of the head assembly of FIG. 8 asviewed from a plane indicated by the line 12-12 in FIG. 9;

FIG. 13 is a schematic enlarged section view of a portion of the headassembly of FIG. 8 that is within a dashed circle labeled FIG. 13 inFIG. 12;

FIG. 14 is a schematic front elevation view of an exemplary embodimentof the rotary knife blade of the power operated dermatome of FIG. 1;

FIG. 15 is a schematic section view of the rotary knife of FIG. 14, asseen from a plane indicated by the line 15-15 in FIG. 14;

FIG. 16 is a schematic enlarged section view of a cutting edge portionof the rotary knife blade shown FIG. 15 that is within a dashed circlelabeled FIG. 16 in FIG. 15;

FIG. 17 is a schematic section view of the power operated dermatome ofFIG. 1, as manipulated to make an initial incision or cut in skin tissuefor a thin type, split thickness skin graft wherein a depth of a layerof skin tissue being excised from a patient or donor graft site is onthe order of 0.005 in. to 0.012 in.;

FIG. 18 is a schematic view, partially in perspective and partially insection, of the power operated dermatome of FIG. 1, as manipulated tocut or excise a thin type, split thickness skin graft wherein a depth ofa layer of skin tissue being excised from a patient or donor graft siteis on the order of 0.005 in. to 0.012 in.;

FIG. 19 is a schematic view, partially in perspective and partially insection, of the power operated dermatome of FIG. 1, as manipulated toterminate an incision in a thin type, split thickness skin graft whereina depth of a layer of skin tissue being excised from a patent or donorgraft site is on the order of 0.005 in. to 0.012 in.;

FIG. 20 is a schematic view, partially in perspective and partially insection, of the power operated dermatome of FIG. 1, as used in a fullthickness skin graft wherein a depth of a layer of skin tissue beingexcised from a donor graft site is on the order of 0.030 in. to 0.043in.;

FIG. 21 is a schematic section view of a portion of the dermatome ofFIG. 1 showing the depth gauge assembly in a fully closed positionproviding a minimum depth of cut of the dermatome; and

FIG. 22 is a schematic perspective view of a second exemplary embodimentof a hand held, power operated dermatome of the present disclosureincluding a handle assembly and a head assembly including a rotary knifeblade and a depth gauge assembly extending into a central, interiorregion defined by the rotary knife blade;

FIG. 23 is a schematic front elevation view of the power operateddermatome of FIG. 22; and

FIG. 24 is a schematic longitudinal section view of the power operateddermatome of FIG. 22, as viewed along a longitudinal axis LA' of thehandle assembly of the dermatome and as seen from a plane indicated bythe line 24-24 in FIG. 23.

DETAILED DESCRIPTION

The present disclosure relates to a hand-held, power operated dermatome100 for medical use in removing a layer of skin tissue SK (FIGS. 17-21)from a patient or donor in connection with various medical proceduresincluding split-thickness and full-thickness skin grafting, skindebriding, e.g., removal of burned skin tissue, tumor/lesion removal,breast reduction, among other procedures, including removing a layer ofskin tissue from a deceased human or animal donor for skingrafting/transplanting purposes. Advantageously, the dermatome 100 ofthe present disclosure includes an annular rotary knife blade 300 thatis driven about a central axis of rotation R at a high rotational speed(on the order of 500-1,500 RPM) by a drive assembly 500 of the dermatome100 and further includes a depth gauge assembly 600 to allow precisesetting and adjustment of a depth of cut DOC of the dermatome 100.

A cutting edge 360 of the rotary knife blade 300 cuts or excises anupper layer of skin tissue SK from a grafting region GR, resulting in anexcised section or layer of skin tissue EST, as illustrated in FIGS.18-20. In the dermatome 100 of the present disclosure, a cutting angleCA (FIGS. 7, 12, 13 and 16) of the blade section 304 adjacent thecutting edge 360 with respect to a cutting plane CP of the rotary knifeblade 300 is relatively shallow. In one exemplary embodiment, thecutting angle CA is approximately 30° with respect to the cutting planeCP. The depth gauge assembly 600 of the dermatome 100 includes anaxially adjustable depth gauge 620. The axially adjustable depth gauge620 includes a depth gauge plate 622 and a depth gauge shaft 640 affixedto the depth gauge plate 622. The depth gauge 620 extends into a centralopening 301 defined by the rotary knife blade 300.

An axial position of the depth gauge plate 622 with respect to thecutting edge 360 of the rotary knife blade 300 is determined by arotation position of a depth adjustment knob 650 of the depth gaugeassembly 600. The axial position of the gauge plate 622 of the depthgauge 620 with respect to the cutting edge 360 of the rotary knife blade300 sets the depth of cut DOC of the dermatome 100. The depth of cut DOCof the dermatome 100 determines the depth or thickness of a section ofskin tissue SK excised by the dermatome 100. The depth or thickness ofan excised skin tissue section or layer is labeled as DEST in FIGS.18-20. That is, the depth or thickness of an excised skin tissue sectionDEST of a patient or donor is determined by the depth of cut DOC of thedermatome 100, as precisely set by the operator of the dermatome 100using the depth adjustment knob 650.

As compared to prior manual or power operated dermatomes, the highrotary speed of the rotary knife blade 300 of the dermatome 100 of thepresent disclosure, in combination with a shallow cutting angle CA ofthe knife blade 300 and configuration of the depth gauge assembly 600and, specifically, the depth gauge plate 622, facilitate an operator'sability to cut or harvest an excised layer of skin tissue EST having adesired depth of cut of the excised tissue DEST that is more uniform andconsistent along a longitudinal extend LE (FIGS. 18 and 19) of theexcised skin tissue EST than what would be expected using a prior manualdermatome or a prior power operated dermatome. The dermatome 100 of thepresent disclosure advantageously provides for improved control andmanipulation of the dermatome 100 by an operator, using one hand, as thedermatome 100 is moved along a path of travel PT to cut the skin tissueSK to produce the excised skin section EST. Moreover, the high rotaryspeed of the rotary knife blade 300 of the dermatome 100 reducesoperator fatigue when removing large sections of skin tissue ST in agrafting region GR. The high rotary speed of the rotary knife blade 300also facilitates making an initial incision (FIG. 17) in a layer of skintissue SK at the cutting edge 360 of the rotary knife blade 300 withoutthe need for applying counter traction to the skin tissue ST in thegrafting region GR.

Advantageously, rotation of the depth adjustment knob 650 of the depthgauge assembly 600 quickly and precisely changes the axial position ofthe depth gauge plate 622 with respect to the cutting edge of the rotaryknife blade 300, thereby allowing the operator to change the depth ofcut DOC of the dermatome 100, as desired. The depth of cut DOC of thedermatome 100 directly determines the resulting excised skin tissuedepth of cut DEST. By way of example and without limitation, thedermatome 100 of the present invention may be advantageously used forsplit thickness skin grafting (schematically depicted in FIGS. 17-19)and full thickness skin grafts (schematically depicted in FIG. 20).Approximate depth or thickness ranges for split thickness skin graftingmay be categorized into three types of split thickness skin grafting: a)thin-type-skin tissue depth range 0.005 in.-0.012 in.; b)intermediate-type-depth range 0.012 in.-0.018 in.; and c)thick-type-depth range 0.018 in-0.030 in. The approximate depth orthickness range for full thickness skin grafting is 0.030 in.-0.043 in.

The dermatome 100 of the present disclosure provides for both rapid andprecise adjustment of the dermatome depth of cut DOC and improvedcontrol and manipulation of the dermatome 100. These features enhancethe ability of an operator to produce an excised skin tissue section ESThaving a desired depth of excised skin tissue DEST and having aconsistent or uniform depth along the longitudinal extent LE of theexcised skin tissue section EST, even when undertaking thin-type,split-thickness skin grafts wherein the desired depth or thickness ofthe excised skin tissue EST is in a range of approximately 0.005 in. to0.012 in. in depth (FIGS. 17-19). Advantageously, the operator need onlykeep the cutting edge 360 of the dermatome 100 flush or flat against theskin tissue ST as the dermatome 100 is moved along its path of travel PTto excise a section of skin tissue EST. This makes the cutting procedureless dependent on operator skill level, as opposed to a cuttingprocedure where the operator was required to maintain a particular angleof the dermatome with respect to the skin tissue as the dermatome ismoved along its path of travel or where the operator was required tochange the angle of the dermatome with respect to the skin tissue as thedermatome is moved along its path of travel. The characteristics of thedermatome 100 of the present disclosure allow an operator to cut excisedskin tissue sections EST of desired depth and substantially uniformdepth from a patient/donor grafting region GR with less dependence onoperator skill and more dependence on the attributes and characteristicsof the dermatome 100.

Moreover, as can be seen in FIG. 5, because the cutting edge 360 of therotary knife blade 300 of the dermatome 100 extends around the entire360° circumference of the rotary knife blade 300, a cutting region ofthe dermatome 100 likewise extends 360° around the cutting edge 360.Thus, unlike prior manual or power operated dermatomes having a straightcutting blade and, therefore, were generally limited to a single cuttingdirection, the dermatome 100 of the present disclosure mayadvantageously used in any desired cutting direction-toward theoperator, away from the operator, parallel to the operator, and anydirection therebetween. Thus, the dermatome 100 of the presentdisclosure can be moved in various directions, as desired by theoperator, to cut skin tissue SK from a grafting region GR, including anatural movement of sweeping the operator's hand and arm in a generallyarcuate path inwardly toward the operator's body, thereby cutting theskin tissue section ST as the dermatome 100 along a generally arcuatepath toward the operator's body. Advantageously, such a “toward theoperator” cutting direction of the dermatome 100 facilitates a clearview of the grafting region GR by the operator. Further, advantageously,the range of cutting directions afforded by the dermatome 100 of thepresent disclosure facilitates maneuvering of the dermatome 100 aroundtight spaces and/or honey prominences in the grafting region GR.

FIRST EXEMPLARY EMBODIMENT Power Operated Dermatome 100

A first exemplary embodiment of a hand-held, power operated dermatome ofthe present disclosure is schematically shown at 100 in FIGS. 1-7. Thepower operated dermatome 100 includes an elongated handle assembly 110and a head assembly 200 extending from a forward or distal end 160 ofthe handle assembly 110. An attachment assembly 120 releasably affixesthe head assembly 200 to the handle assembly 110. As is best seen inFIGS. 8-13, the head assembly 200 includes a frame body or frame housing202, the rotary knife blade 300, an annular blade housing assembly 400which rotatably supports the rotary knife blade 300 for rotation aboutthe central axis of rotation R and the depth gauge assembly 600. Theblade housing assembly 400 includes an annular blade housing 410 and ablade lock ring 450 which is releasably affixed to the blade housing 410to trap and secure the rotary knife blade 300 for rotation with respectto the blade housing assembly 400. As is best seen in FIGS. 14-16, therotary knife blade 300 includes a body section 302, a blade section 304and a continuous rolling bearing structure 370 defining a portion of anouter peripheral surface 369 (FIG. 13) of the rotary knife blade 300. Ascan best be seen in FIG. 17, the continuous rolling bearing structure370 is permanently affixed to a concave bearing surface 319 of therotary knife blade body section 302 and, in turn, defines a convexbearing surface 380 of the rotary knife blade 300.

As can be seen schematically in FIG. 7, the rotary knife blade 300 isrotated with respect to the blade housing assembly 400 about the centralaxis of rotation R by a drive assembly 500 which includes a drive motorassembly 501 and a gear train 520. In one exemplary embodiment, thedrive motor assembly 501 is supported by the handle assembly 110, whilethe gear train 520 is supported by a gearbox housing 203 of the framebody 202 of the head assembly 200. The depth gauge assembly 600 is alsosupported by the frame body 202 and includes a depth gauge support 602.The depth gauge support 602, which extends from the frame body 202, inturn, supports the depth gauge 620 including the depth gauge plate 622and depth gauge shaft 640. The depth gauge 620 extends into the centralinterior region 301 of the rotary knife blade 300.

Handle Assembly 110 & Attachment Assembly 120

As can best be seen in FIGS. 1-5 and 7, the handle assembly 110 extendsbetween the forward or distal end 160 and a rearward or proximal end 162and includes an elongated handle 112 and a proximal or rear handle cover170. The handle assembly 110 establishes and extends along alongitudinal axis LA. The longitudinal axis LA of the handle assembly110 establishes a longitudinal axis of the dermatome 100. In oneexemplary embodiment, the handle assembly longitudinal axis LA issubstantially orthogonal to and intersects the central axis of rotationR of the rotary knife blade 300. An outer surface 113 of the handle 112is contoured for easy gripping by the operator. The handle 112 includesa generally cylindrical, longitudinal throughbore 114 which supports thedrive motor assembly 501 of the drive assembly 500. A forward or frontend 116 of the handle 112 includes a radially inwardly stepped portion118 that serves as an attachment point for the attachment assembly 120.

In one exemplary embodiment, the drive motor assembly 501 is actuated bya combination of an actuation lever 150 which is pivotally mounted withrespect to the handle 112, a lever sensing switch 151, and an actuationswitch 152. When the actuation lever 150 is pivoted to an “on” position,generally parallel to the outer surface 113 of the handle 112, a leversensing switch 151 disposed within the handle throughbore is tripped. Anactuation switch 152 is located on the cover 170 at the proximal end 162of the handle assembly 110. When the actuation lever 150 is pivoted tothe “on” position and the actuation switch 152 is pressed within fiveseconds of the tripping of the lever sensing switch 151, the driveassembly 500 is actuated to rotate the rotary knife blade 300. If theactuation switch 152 is not pressed within five seconds of the trippingof the lever sensing switch 151, the actuation lever 150 must bereleased and again pivoted to the “on” position. Alternately, the drivemotor assembly 501 may be actuated by a foot pedal valve positioned atthe feet of the operator affixed to the handle assembly 110 or a toggleor rocker switch mounted on the handle assembly 110.

The handle assembly 110 extends orthogonally in a rearward direction RW(FIG. 7) away from the head assembly 200 along the handle axislongitudinal axis LA. The longitudinal axis LA is substantiallyorthogonal to the blade central axis of rotation R and parallel to thecutting plane CP of the rotary knife blade 300. This configurationallows the operator of the dermatome 100 to wield and manipulate thedermatome 100 effectively using one hand. The rear handle cover 170 ofthe handle assembly 110 overlies a proximal end of the handle 112 and iscoupled to an air line or air hose 180 which provides a source of highpressure air to provide motive power to the drive motor assembly 501.

The attachment assembly 120 includes a coupling collar 122, a retainer128 and an inner sleeve 130 that attaches to the inwardly steppedportion 118 at the front end 116 of the handle 112. The coupling collar122 includes an inner surface 124 having a threaded portion 126. As canbest be seen in FIG. 7, the coupling collar 122 is rotatably secured tothe handle 112 by the retainer 128 and the inner sleeve 130. In turn,the coupling collar 122 threads onto a threaded outer surface 230 of theframe body 202 to releasably secure the head assembly 200 to the forwardend 160 of the handle assembly 110. Advantageously, the attachmentassembly 120 allows for easy coupling and decoupling of the headassembly 200 from the handle assembly 110 to facilitate disassembly andsterilization of components of the head assembly 200 upon completion ofa skin grafting or other medical procedure performed with the dermatome100.

As used herein, axial, upper and lower shall mean movement or adimension in a direction generally along or parallel to an extent of thecentral axis of rotation R. Forward or distal shall mean in a directiongenerally along a direction labeled FW in FIG. 7, the forward directionFW being generally parallel to or along the longitudinal axis LA.Rearward or proximal shall mean a direction generally along a directionlabeled RW (opposite of the forward direction FW) in FIG. 7.

Drive Assembly 500

As best seen in FIG. 7, the drive assembly 500 includes the drive motorassembly 501 and the gear train 520. The present disclosure contemplatesat least three different drive motor assemblies, an air motor embodiment(schematically shown in FIG. 7) and, alternatively, an electric motordisposed in the handle assembly (not shown), and a flexible drive shaftembodiment (not shown) to provide motive power to rotate the rotaryknife blade 300 within the blade housing assembly 400. In one exemplaryembodiment, the drive motor assembly 501 includes a vane-type air orpneumatic motor 502 and a planetary gear reduction unit 504 disposedwithin the longitudinal throughbore 114 of the handle 112. High pressureair is communicated via the air hose 180 coupled to the cover 170 at theproximal end 162 of the handle assembly 110 and directed into the motor502. The air is routed through the motor body and directed against aplurality of vanes to rotate a rotor of the motor 502. The rotorincludes an output shaft 503 coupled to the planetary gear reductionunit 504. The planetary gear reduction unit 504 serves to convert thehigh rotational speed of the rotor shaft to a drive coupling 506 thatrotates at a lower speed but a higher torque output than the rotor shaft503.

In one exemplary embodiment, the gear train 520 comprises a pinion gear522 (FIG. 2). An input shaft 524 at a proximal end of the pinion gear522 receives the drive coupling 506 of the drive motor assembly 501. Thepinion gear 522 includes a gear head 526 at its distal end. In oneexemplary embodiment, the gear head 526 defines a bevel gear 528including a set of bevel gear teeth 530. The pinion gear 522 issupported for rotation in the gearbox housing 203 of the frame body 202about a pinion gear axis of rotation PGR (FIG. 7) and is positioned suchthat the set of bevel gear teeth 530 of the pinion gear 522 meshes witha mating set of bevel gear teeth 330 of a driven gear 328 of the rotaryknife blade 300. The gear head 526 of the pinion gear 522 engages anddrives the driven gear of the rotary knife blade 300 to rotate the blade300 about its axis of rotation R.

As can be seen in FIG. 7, the pinion gear axis of rotation PGR issubstantially congruent with the handle assembly longitudinal axis LA.As the drive coupling 506 of the drive motor assembly 501 rotates thepinion gear 522 within the gearbox housing 203. Rotation of the piniongear 522, in turn, rotates the rotary knife blade 300 about its axis ofrotation R. A suitable pneumatic motor/planetary gear reduction unitconfiguration is disclosed in U.S. patent application Ser. No.13/073,207 to Whited et al., filed Mar. 28, 2011, and entitled PowerOperated Rotary Knife With Disposable Blade Support Assembly (“the '207application”). The '207 application is assigned to the assignee of thepresent application and is incorporated herein, in its entirety, byreference.

Alternatively, the drive motor assembly 501 may comprise an externaldrive motor, for example, an external brushless DC servo motor, and aflexible shaft drive transmission (not shown). The drive motor assemblyrotates a drive shaft of a flexible shaft drive transmission. A portionof the flexible shaft drive transmission extends through thelongitudinal throughbore 114 of the elongated handle 112 of the handleassembly 110. A suitable DC motor/flexible drive shaft transmissionconfiguration is disclosed in U.S. patent application Ser. No.13/344,760 to Rapp et al., filed Jan. 6, 2012, and entitled FlexShaft-Drive Motor Connection For Power Operated Rotary Knife (“the '760application”). The '760 application is assigned to the assignee of thepresent application and is incorporated herein, in its entirety, byreference.

Alternately, the drive motor assembly 501 may comprise an electric drivemotor disposed within the longitudinal throughbore 114 of the handle112. In one exemplary embodiment, the electric drive motor is a DCmotor. A suitable DC electric motor, for example, the Maxon Model No.EC22 386680 and an associated gear reduction unit, for example, theMaxon Model No. GPM 22M 305130, may be obtained from Maxon Motor AG,Sachsein, Switzerland (www.maxonmotor.com).

Head Assembly 200

Turning to FIGS. 8-13, the head assembly 200 of the power operateddermatome 100 of the present disclosure includes the frame body 202, therotary knife blade 300, the annular blade housing assembly 400, and thedepth gauge assembly 600. In the dermatome 100, both the depth gaugeassembly 600 and the blade housing assembly 400 are supported by andextend from the frame body 202. The depth gauge plate 622 of the depthgauge assembly 600 extends into the interior region 301 of the rotaryknife blade 300. A lower edge region 634 of the depth gauge plate 622,in combination with the cutting edge 360 of the rotary knife blade 300,determine the depth of cut DOC of the dermatome 100.

Frame Body 202

As best seen in FIGS. 8-13, the frame body 202 includes a rearwardhandle attachment portion 204 and a forward interface portion 206. Therearward handle attachment portion 204 comprises a generally cylindricalbody 205 defining the threaded outer surface 230 of the frame body 202.The threaded outer surface 230 of the frame body cylindrical body 205 isengaged by the attachment assembly 120 to releasably affix the headassembly 200 to the handle assembly 110.

The frame body 202 includes a gearbox housing 203 which rotatablysupports gear train 520 of the drive assembly 500, specifically, thepinion gear 522. The gearbox housing 203 includes an inner surface 208of the frame body 202. The inner surface 208 defines a longitudinallyextending throughbore 209. As seen in FIG. 7, the pinion gear 522 isseated in the throughbore 209. A front opening 232 (FIGS. 11 and 12) ofthe throughbore 209 is configured to allow the gear head 526 of thepinion gear 522 to engage the driven gear 328 of the rotary knife blade300. A rear opening 234 (FIGS. 9 and 12) of the throughbore 209 allowsentry of the drive coupling 506 of the drive motor assembly 501 into thepinion gear input shaft 524 when the head assembly 200 is releasablyaffixed to the handle assembly 110.

The forward interface portion 206 of the frame body 202 includes anupper interface region 220 that extends or transitions between thecylindrical body 205 of the rearward handle attachment portion 204 andthe central cylindrical support 602 of the depth gauge assembly 600. Inone exemplary embodiment, the upper interface region 220, when viewedfrom above in plan view, comprises a generally V-shaped rib 222 whereinthe V-shaped rib 222 is widest adjacent to the cylindrical body 205 andtapers or converges in a direction proceeding toward the centralcylindrical support 602, that is, the central cylindrical support 602can be viewed as serving as a termination or vertex of the rib 222.Thus, the central cylindrical support 602 of the depth gauge assembly600 is attached to and extends from the frame body 202 and, morespecifically, the depth gauge assembly 600 is attached to and extendsfrom the upper interface region 220 of the frame body 202.

Positioned axially below the upper interface region 220 is a lowerinterface region 210 that extends or transitions between the cylindricalbody 205 of the rearward handle attachment portion 204 and the annularblade housing 410 of the blade housing assembly 400. In one exemplaryembodiment, the lower interface region 210, when viewed from below inplan view, comprised a Y-shaped support 212 that includes arms thatextend circumferentially about the annular blade housing 410. Thus, theannular blade housing 410 of the blade housing assembly 400 is attachedto and extends from the frame body 202 and, more specifically, the lowerinterface region interface region 220 of the frame body 202.

Rotary Knife Blade 300

As can best be seen in FIGS. 14-17, in one exemplary embodiment, theannular rotary knife blade 300 includes an inner wall 365 and an outerwall 366 and a first upper end 367 and a second lower end 368. The innerwall 365 defines the open, interior region 301 of the rotary knife blade300. The rotary knife blade 300 includes the upper body section 302, thelower blade section 304 and the continuous rolling bearing structure370. The continuous rolling bearing structure 370 forms a portion of aperipheral outer surface 303 of the body section 302 and defines theconvex bearing surface 380 of the rotary knife blade 300. The upper bodysection 302 extends between a first upper end 306 and a second lower end308. The upper end 306 corresponds to and is congruent with the firstupper end 367 of the rotary knife blade 300. A radially extendingshoulder 308 a between the body section 302 and the blade section 304defines the second lower end 308 of the body 302. The body section 302includes an inner wall 310 and a radially spaced apart outer wall 312.The first upper end 306 of the body section 302 defines the driven gear328 of the rotary knife blade 300. The driven gear 328 comprises the setof bevel gear teeth 330 that operatively engage and mesh with the bevelgear 528 of the pinion gear 522, as previously discussed, such thatrotation of the bevel gear 528 results in rotation of the rotary knifeblade 300 about its axis of rotation R.

The body section 302 of the rotary knife blade 300 includes a bearingsurface 319 formed in the outer wall 312 of the body 302. In oneexemplary embodiment, the bearing surface 319 comprises a bearing race320 that extends radially inwardly into the outer wall 312. The bearingrace 320 includes a generally convex arcuate bearing face 322. Thebearing face 322 provides a seating surface for the continuous rollingbearing structure 370 of the rotary knife blade 300. The continuousrolling bearing structure 370 defines the convex bearing surface 380 ofthe rotary knife blade 300 that projects radially outwardly from theouter wall 312 of the body section 302 of the blade 300 and therebyforms a portion of a peripheral outer surface 303 of the body section302 and forms a portion of a peripheral outer surface 369 of the rotaryknife blade 300. The continuous rolling bearing structure 370rotationally supports the rotary knife blade 300 with respect to theblade housing assembly 400.

The continuous rolling bearing structure 370 comprises an annularrolling bearing strip 372 that extends continuously 360° around theperiphery of the outer wall 312 of the body section 302 and is disposedin the bearing race 320. The rolling bearing strip 372 includes aplurality of spaced apart ball bearings 376 rotatably supported inradially spaced apart pockets of a separator cage 378. In one exemplaryembodiment, the separator cage is flexible and a diameter of each of theball bearings 376 is approximately 2 mm., although it should beunderstood that the diameter could be larger or smaller. Portions of theplurality of ball bearings 376 extend radially outwardly from the outerwall 310 of the blade body section 302 and thus form a part of the outerperiphery 303 of the body section 302. Specific details concerning thestructure and configuration of the plurality of spaced apart ballbearings and the flexible separator cage are disclosed in U.S. patentapplication Ser. No. 13/189,951, filed Jul. 25, 2011 to Whited et al.,and entitled Power Operated Rotary Knife (“the '951 application”). The'951 application is assigned to the assignee of the present applicationand is incorporated herein, in its entirety, by reference.

The rolling bearing strip 372 is disposed in an annular gap G definedbetween opposing faces of the rotary knife blade 300, the blade housing410 and a blade lock ring 450 of the blade housing assembly 400, in theregion of the rotary knife blade bearing race 320. Specifically, theplurality of ball bearings 376 of the rolling bearing strip 372 aredisposed within an annular passageway 374, which is circular in crosssection and defined by the opposing arcuate bearing surfaces 319, 426,458 of the rotary knife blade 300, the blade housing 410 and the bladelock ring 450, respectively.

By virtue of the annular rolling bearing strip 372 being continuous anddisposed within the bearing race 320, the strip 372 is permanentlyaffixed to and thus is part of the blade 300. However, as the pluralityof ball bearings 376 of the rolling bearing strip 372 contact the bladebearing race 320, the rolling bearing may rotate with respect to theblade body 302 and the blade section 304 of the blade 300. When rotaryknife blade 300 is rotated by the drive assembly 500 and, specifically,the pinion gear 522, at a specific, desired RPM, the separator cage 378also moves or translates in a circle along the annular gap G, althoughthe rotational speed of the separator cage 378 within the gap G is lessthan the RPM of the rotary knife blade 300. Thus, when the dermatome isin operation, the continuous, annular rolling bearing strip 372traverses through the annular passageway 374 forming a circle about theknife blade axis of rotation R. Similarly, when the dermatome 100 is inoperation, the separator cage 378, due to its movement or translationalong the annular gap G about the knife blade axis of rotation R, can beconsidered as forming a complete cylinder within the gap G.Additionally, when the rotary knife blade 300 is rotated, the pluralityof ball bearings 376 both rotate with respect to the separator cage 378and also move or translate along the annular passageway 374 about theknife blade axis of rotation R as the separator cage 378 moves ortranslates along the annular gap G. A plane passing through therespective centers of the plurality of ball bearings 376 define arotational plane RP (FIGS. 13 and 15) of the rotary knife blade 300. Therotational plane RP of the rotary knife blade 300 is substantiallyparallel to the cutting plane CP of the blade 300 and substantiallyorthogonal to the axis of rotation R of the blade 300.

The rotary knife blade 300 also includes the blade section 304 extendingbetween a first upper end 350 (adjacent the shoulder 308 a of the bodysection 302) and a second lower end 352. The second lower end 352corresponds to and is congruent with the lower end 368 of the rotaryknife blade 300. The blade section includes an inner wall 354 and aradially spaced apart outer wall 356. The inner and outer walls 354, 356are generally parallel and frustoconical, converging in a directionproceeding downwardly or toward the cutting edge 360 of the blade. Thecutting edge 360 of the rotary knife blade 300 is generally circular.The inner wall 310 of the body section 302 and the inner wall 354 of theblade section 304 combine to form the inner wall 365 of the rotary knifeblade 300 and define the interior region 301 of the blade 300. Theinterior region 301 of the rotary knife blade is generallyfrustoconical, converging in a direction toward the cutting edge 360 ofthe blade 300. A plane aligned with the generally circular cutting edge360 of the rotary knife blade 300 defines the cutting plane CP (FIG. 15)of the blade 300.

In one exemplary embodiment, the blade section 304 includes an upperregion 358 and a lower region 359 separated by a knee or discontinuitybetween the two regions. Of course, it should be recognized that theblade section 304 may comprise a single region with no discontinuity.The lower region 359 defines the cutting angle CA of the blade and isdefined by an angle between the inner wall 354 in the lower region 359of the blade section 304 and the cutting plane CP. In one exemplaryembodiment, the cutting angle CA is approximately 30°, although itshould be understood that the cutting angle CA could be greater orsmaller. As can be best seen in FIG. 16, the lower end 352 of the bladesection 304 which defines the cutting edge 360, includes a short sectionof wall 362 bridging the inner and outer walls 354, 356. The cuttingedge 360 is formed at the intersection of the short section of wall 362and the inner wall 354. The short section of wall 362 is slightly angledwith respect to the cutting plane CP, at about 5° in one exemplaryembodiment, to provide relief for the cutting edge 360.

In one exemplary embodiment, the inner diameter (defined by the cuttingedge 360) of the rotary knife blade 300 is approximately 4.000 in.,while the outer diameter (defined by the outer periphery of theplurality of ball bearings 376 the rolling bearing strip 372 isapproximately 5.189 in., although it should be understood that thediameters could be larger or smaller.

Blade Housing Assembly 400

As can best be seen in FIGS. 10-13 and 16-17, the blade housing assembly400 includes the annular blade housing 410 and the blade lock ring 450.The annular blade housing 410 extends from and is supported by theY-shaped support 212 of the lower interface region 210 of the forwardinterface portion 206 of the frame body 202. The blade housing 410includes a first upper end 412 and an axially spaced apart second lowerend 414. The blade housing 410 further includes an inner wall 416 and aradially spaced apart outer wall 418. The blade housing 410 includesthree peripherally spaced apart threaded openings 430 of the bladehousing 410. The three threaded openings 430 extend from the secondlower end 414 through the first upper end 412. The inner wall 416 of theblade housing 410 includes a bearing surface 420. In one exemplaryembodiment, the bearing surface 420 comprises a bearing race 422 thatextending radially inwardly into the inner wall 416 of the blade housing410. The bearing race 422 includes the concave, arcuate bearing surfaceor face 426.

As can be best be seen in FIGS. 13, 17 and 18, in axial extent, thearcuate bearing face 426 is a curved bearing surface that extends froman upper region 376 a of the ball bearing 376 and generally conforms tothe curvature of the ball bearing 376 to about a midpoint 376 b of theball bearing 376. The arcuate bearing face 426 does not, however, extendall the way to a lower region 376 c of the ball bearing 376. Instead, anarcuate bearing surface or face 458 formed on an inner surface 456 ofthe blade lock ring 450 constitutes a portion of a total bearing race470 (FIGS. 17 and 18) provided by the blade housing assembly 400. Thetotal bearing race 470 defined by the blade housing assembly 400 resultsfrom a combination of the bearing surfaces of the blade housing 410 andthe blade lock ring 450, specifically, the arcuate bearing face 426 ofthe blade housing 410 and the arcuate bearing face 458 of the blade lockring 450. The total bearing race 470 serves as an arcuate bearingsurface for the annular rolling bearing strip 372 of the rotary knifeblade 300 when the blade lock ring 450 is secured to the blade housing410 and the rotary knife blade 300 is captured or sandwichedtherebetween.

The blade lock ring 450 includes an upper surface 451 and a lowersurface 452 and comprises an upper seating region 453 and a radiallyinwardly offset lower bearing region 454. The upper seating region 453seats flush against the blade housing 410 and includes threeperipherally spaced apart slots 462 in an outer periphery 460 of theblade lock ring 450. The blade lock ring 450 adapted to be secured to astepped shoulder 415 (FIG. 18) near the lower end 414 of the bladehousing 410. The blade lock ring 450 is secured to the stepped shoulder415 of the blade housing 410 via three threaded fasteners 464, each ofwhich passes through a correspond peripherally spaced apart slot 462 inan outer periphery 460 of the blade lock ring 450.

To install or affix the rotary knife blade 300 to the blade housingassembly 400, with the blade lock ring removed, the head assembly 200 isturned upside down and the rotary knife blade 300 is placed in theupside down blade housing 410. The plurality of ball bearings 376 of therotary knife blade 300 rest on the bearing race 422 of the blade housing410 thereby the rotary knife blade 300 is supported by the blade housing410. The three slots 462 of the blade lock ring 450 are aligned with thethreaded openings 430 of the blade housing 410. The three threadedfasteners 464 pass through the slots 462 and are threaded into thethreaded openings 430 of the blade housing 410 to complete theinstallation. Because of the configuration of the three slots 462, it isonly necessary to loosen the three threaded fasteners 464 a sufficientamount to rotate the blade lock ring 450 with respect to the bladehousing 410. This allows the blade lock ring 450 to be removed from theblade housing 410 without removing the three threaded fasteners 464 fromthe threaded openings 430 of the blade housing 410. When the blade lockring 450 is removed from the blade housing 410 turning the head assembly200 upside down causes the rotary knife blade 300 to fall out of theblade housing 410 thereby removing the blade 300 from the blade housingassembly 400.

Depth Gauge Assembly 600

As can best be seen in FIGS. 10-13 and 17-21, the depth gauge assembly600 includes the depth gauge support 602 and the depth gauge 620. Thedepth gauge 620 includes the depth gauge shaft 640 and the depth gaugeplate 622. The depth gauge assembly 600 further includes the depthadjustment knob 650, a stop ring 670, a biasing spring 680 and a dowelpin 690 (FIGS. 10 and 11). Advantageously, the depth gauge assembly 600permits an operator to quickly and accurately change the depth of cutDOC of the dermatome from essentially 0.000 in. (no depth of cut of skintissue ST—shown schematically in FIGS. 21) to 0.045 in. (full depth ofcut of skin tissue ST—shown schematically in FIGS. 12 and 20).Obviously, the range of depth of cut DOC may be changed based on theconfiguration of the depth gauge assembly 600 and the present inventionis not limited to the exemplary depth of cut range set forth herein. Aschanging the depth of cut DOC of the dermatome 100 is accomplished byrotation of the depth adjustment knob 650, the depth of cut DOC isinfinitely variable between the 0.000 in. and 0.045 in. endpoints. Thatis, the operator can precisely dial in an exact desired depth of cut DOCfor the dermatome 100.

Depth Gauge Cylindrical Support 602

As best seen in FIGS. 8 and 10-12, the depth gauge cylindrical support602 extends from and is supported by the V-shaped rib 222 of the upperinterface region 220 of the forward interface portion 206 of the framebody 202. The depth gauge support 602, in one exemplary embodiment, isgenerally cylindrical and includes an upper end 604 and an axiallyspaced apart lower end 606. The depth gauge cylindrical support 602defines an axially extending central opening 608 (FIG. 12) passingthrough the support 602. A radially outwardly extending flange 610 isdisposed at the upper end 604 of the depth gauge cylindrical support602. As can be seen in FIG. 10, the flange 610 includes a first smalleropening 612 that is axially aligned with the central opening 608 and asecond larger opening 614 that is connected to but offset from the firstsmaller opening 612. A radially outwardly extending slot 616 (FIG. 12)is disposed between the flange 610 and the central opening 608 of thedepth gauge cylindrical support 602.

An upper surface 618 of the flange 610 includes indicia or markings 619(FIG. 10) representing gradations for the depth of cut DOC of thedermatome 100 as the depth adjustment knob 650 is rotated. Specifically,each of the smaller gradations represent a change in the set depth ofcut DOC of 0.001 in., while the larger gradations represent a change inthe set depth of cut of 0.005 in. The indicia 619 facilitate precisesetting of the dermatome depth of cut DOC by the operator.

The depth gauge shaft 640 is received in the axially extending centralopening 608 of the cylindrical support 602. The depth gauge shaft 640 issupported by the cylindrical support 602 for axial movement with respectto the cylindrical support 602. Specifically, the cylindrical support640 contacts and supports the depth gauge shaft 640 over an axial lengthlabeled AL in FIG. 12. In one exemplary embodiment, the axial length ALof the cylindrical support 602 is approximately 1.05 in., while theoverall axial length of the cylindrical support 602 extending betweenthe upper end 604 of the cylindrical support 602 and the lower end 606of the cylindrical support 602 is approximately 1.25 in.

Depth Gauge 620

The depth gauge 620 is supported by the depth gauge support 602 andincludes the depth gauge plate 622 and the depth gauge shaft 640. As canbe seen in FIG. 12, the depth gauge shaft 640 and the depth gauge plate622 are substantially concentric with the knife blade axis of rotationR. The depth gauge 20 is adjustable to move axially along the axis ofrotation R, that is, the depth gauge moves axially respect to the depthgauge support 602 and with respect to the cutting plane CP of the rotaryknife blade 300. Movement of the depth gauge plate 622 with respect tothe cutting plane CP of the rotary knife blade 300 changes the dermatomedepth of cut DOC. The depth gauge plate 622 and a portion of the depthgauge shaft 640 extend into the interior region 301 of the rotary knifeblade 300. The depth gauge 620 also includes the stop ring 670 which isaffixed to an upper end of the depth gauge shaft 640 and moves with theshaft 640 axially to limit downward movement of the depth gauge 620.That is, the stop ring 670 insures that the minimum depth of cut DOC is0.000 in., as opposed to the depth gauge plate 622 moving in a downwarddirection DW to a negative depth of cut DOC position.

Depth Gauge Plate 622

The depth gauge plate 622 is generally disc-shaped and includes an uppersurface 623 and an axially spaced apart generally planar lower surface624. The depth gauge plate 622 includes a central body 626 and aradially outwardly spaced annular rim 628. The central body 626 and theannular rim 628 are connected by three radially extending ribs 630. Thecentral body 626 of the depth gauge plate 622 includes a central opening627 that receives a lower connecting end 642 of the depth gauge shaft640 to secure the depth gauge plate 622 to the depth gauge shaft 640.

The depth gauge plate 622 includes a radially outer peripheral surface632. A lower edge region 634 of the depth gauge plate 622 is anintersection region between the planar lower surface 624 of depth gaugeplate 622 and outer peripheral surface 632 of depth gauge plate. At anyaxial position of the depth gauge plate 622, the lower edge region 634of the depth gauge plate 622 is the closest portion of the depth gauge622 to the cutting edge 360 of the rotary knife blade 300. The loweredge region 634 is nearly (but not exactly) axially aligned with therotary knife blade cutting edge 360. As such, an axial distance betweenthe lower edge region 634 of the depth gauge plate 622 and the cuttingedge 360 of the rotary knife blade 300 determines the depth of cut DOCof the dermatome 100. Recall that the cutting edge 360 defines thecutting plane CP of the rotary knife blade 300, therefore, statedanother way, an axial distance AD (FIG. 18) between the lower edgeregion 634 of the depth gauge plate 622 and the cutting plane CP of therotary knife blade 300 determines the depth of cut DOC of the dermatome100.

Depth Gauge Shaft 640

As best seen in FIG. 12, the depth gauge shaft 640 is generallycylindrical and includes the lower connecting end 642 that is receivedin the central opening 627 of the central body 626 of the depth gaugeplate 622 to attach the depth gauge shaft 640 and the depth gauge plate622. The depth gauge shaft 640 includes a reduced diameter threadedupper portion 643. When the depth gauge shaft 640 is inserted into theaxially extending central opening 608 of the depth gauge support 602,first, the second threaded portion 648 of the depth gauge shaft 640 isthreaded into the central threaded opening 656 of the depth adjustmentknob 650, then, the stop ring 670 is threaded onto the upper threadedportion 643 of the depth gauge shaft 640 to secure the depth gauge shaft640 (and attached depth gauge plate 622) to the depth gauge support 602.When it is desired to remove the depth gauge shaft 640 from the depthgauge support 602, the stop ring 670 is unthreaded and removed from thedepth gauge shaft 640 and the depth gauge shaft 640 is unthreaded fromthe central threaded opening 656 of the depth adjustment knob 650,allowing the depth gauge shaft 640 to drop out of the depth gaugesupport 602 for cleaning/sterilization purposes.

The depth gauge shaft 640 includes an outer surface 647 defining anaxially extending slot 646. The axially extending slot 646 receives thedowel pin 690 (FIGS. 10 and 11) that passes through a radial opening 617in the depth gauge cylindrical support 602 to prevent relative rotationbetween the depth gauge shaft 640 as supported within the cylindricalsupport 602. The depth gauge shaft 640 also includes a second threadedportion 648 that is disposed below the threaded upper portion 643. Thesecond threaded portion 648 of the depth gauge shaft 640 is threadedlyreceived in a threaded central opening 656 of the depth adjustment knob650.

Depth Adjustment Knob 650

The depth adjustment knob 650 includes an upper end 652 and a lower end654. The depth adjustment knob 650 includes a central threaded opening656 which is threaded onto the second threaded portion 648 of the depthgauge shaft 640. The dowel pin 690 and the axially extending slot 646 ofthe depth gauge shaft 656 allow the depth gauge shaft 656 to moveaxially within the axially extending central opening 608 of the depthgauge cylindrical support 602. The depth adjustment knob 650, whenrotated, drives the depth gauge shaft 656 upward or downward withrespect to the depth gauge cylindrical support 602.

The depth adjustment knob 650 includes a central stem 660, an enlargedupper head 658 above the stem 660, and an enlarged lower head 664 belowthe stem 660. The enlarged lower head 664 is sized to pass though thelarger offset opening 614 of the flange 610 of the depth gaugecylindrical support 602 and is received in the slot 616 of thecylindrical support 602 to restrain axial movement between the depthadjustment knob 650 and the cylindrical support 602. The enlarged upperhead 658 of the depth adjustment knob 650 includes a recessed contactsurface 666 that is configured to be contacted by a lower surface 674 ofthe stop ring 670. An upper surface of the enlarged upper head 658 willinclude an arrow or some other marking that can be aligned with theindicia 619 marked on the upper surface 618 of the cylindrical supportflange 610 to aid the operator in adjusting and setting the depth of cutDOC of the dermatome 100.

As the depth adjustment knob 650 is rotated by the operator, the dowelpin 690 extending into the axially extending slot 646 prohibits thedepth gauge shaft 640 and the depth gauge plate 622 from rotating withthe depth adjustment knob 650. The dowel pin/axially extending slotconfiguration 690/646 does permit the depth gauge shaft 640 to move upand down axially within the depth gauge cylindrical support 602 tochange the depth of cut DOC of the dermatome 100. However, the depthgauge shaft 640 is constrained from rotating with the depth adjustmentknob 650 by virtue of the dowel pin 690 fitting into the axiallyextending slot 646. The depth gauge shaft 640 is constrained fromrotating with the depth adjustment knob 650 and the knob 650 isconstrained from axial movement by virtue of the enlarged lower head 664of the knob 664 being confined in the radially outwardly extending slot616 of the depth gauge cylindrical support 602. Thus, rotation of thedepth adjustment knob 650 drives the depth gauge shaft 640 axially inthe upward direction UP or the downward direction DW with respect to thedepth gauge cylindrical support, depending on the direction of rotationof the depth adjustment knob 650.

When depth adjustment knob 650 is rotated to move the depth gauge 620 inthe downward direction DW, the dowel pin 690 prevents rotation of thedepth gauge 620 with the depth adjustment knob 650. Thus, depending onthe direction of rotation of the depth adjustment knob 650, the depthgauge 620 will be moved in the upward direction UP or the downwarddirection DW with respect to the cylindrical support 602 and the rotaryknife blade 300. Movement of the depth gauge 620 in the upward directionis limited by contact between the upper surface 645 of the centralportion 644 of the depth shaft 640 and a lower end 654 of the depthadjustment knob 650 such that a maximum depth of cut DOC is 0.045 in.This maximum depth of cut DOC configuration is shown in FIGS. 12 and 13and is referred to as the fully open position of the dermatome 100.

Movement of the depth gauge in the downward direction DW is limited bycontact between the lower surface 674 of the stop ring 670 and therecessed contact surface 666 of the enlarged upper head 658 of the depthadjustment knob 650. This minimum depth of cut DOC configuration isshown in FIG. 21 and is referred to as the fully closed position of thedermatome 100. The biasing spring 680 is trapped between the centralbody 626 of the depth gauge plate 622 and the lower end 606 of the depthgauge cylindrical support 602 to bias the depth gauge 620 to the fullyclosed position.

In one exemplary embodiment, the handle assembly 110 may be fabricatedof plastic or other material or materials known to have comparableproperties and may be formed by molding and/or machining The attachmentassembly 120, the frame body 202, and the depth gauge assembly 600 maybe fabricated of aluminum or stainless steel or other material ormaterials known to have comparable properties and may be formed/shapedby casting and/or machining The rotary knife blade 300 and the bladehousing assembly 400 may be fabricated of a hardenable grade of alloysteel or a hardenable grade of stainless steel, or other material ormaterials known to have comparable properties and may be formed/shapedby machining, forming, casting, forging, extrusion, metal injectionmolding, and/or electrical discharge machining or another suitableprocess or combination of processes.

Operation Of Dermatome 100

FIGS. 17-19 schematically illustrate use of the dermatome 100 of thepresent disclosure for excising a layer skin tissue ST in a donorgrafting region GR and, in particular, obtaining a thin type, splitthickness skin graft wherein a depth of a layer of skin tissue beingexcised from the graft region GR is on the order of 0.005 in. to 0.012in. FIG. 17 schematically shows the initial incision into an upper layeror surface SST of the skin tissue ST with the dermatome 100. Recall thatin the illustrated and exemplary embodiment, the cutting angle CA of therotary knife blade 300 is approximately 30°. In making the incision intothe skin tissue surface SST, the angle of the dermatome 100 ismanipulated such that a skin tissue cutting angle STCA is shallower thanthe cutting angle CA of the knife blade 300. In one exemplaryembodiment, the cutting angle of the inner wall 310 in the lower region359 of the blade section 304 adjacent the cutting edge 360 with respectto the surface SST of the skin tissue ST being excised lower isapproximately 15°. Thus, the skin tissue cutting angle STCA(approximately) 15° is less than the blade cutting angle CA.(approximately)30°. Thus, the outer wall 418 of the blade housing 410 isnot vertical, but rather is slightly angled downwardly toward the skintissue ST.

FIG. 18 schematically shows the cutting or excising of the skin tissueST. As the actuated dermatome 100 moves along a path of travel PT, thedermatome 100 produces an excised section of skin tissue EST which flowsalong the inner wall 365 and through the central interior region 301 ofthe rotary knife blade 300 and slanted or frustoconical upper portion ofthe blade housing inner wall 416. The slanted upper portion of the bladehousing inner wall 416 generally continues the frustoconical inner wall365 of the rotary knife blade 300. The excised section of skin tissueEST is a flexible, generally rectangular piece or section of skin tissueST that exits the dermatome 100 by moving or “flopping” (since the skintissue is flexible or flaccid) over the upper end or wall 412 of theblade housing 410. As schematically depicted in FIG. 18, a longitudinalextent LE of the excised section EST, a depth or thickness of excisedskin tissue DEST should be uniform and should conform in thickness tothe depth of cut DOC set by the operator of the dermatome 100. In movingalong the path of travel PT, the angle of the dermatome 100 is heldrelatively flat, that is, the skin tissue cutting angle STCA isapproximately equal to the rotary knife blade cutting angle CA. The skintissue cutting angle STCA and the rotary knife blade cutting angle CAboth being approximately 30°. Advantageously, the operator need onlykeep the cutting plane CP of the dermatome 100 flush or flat against thesurface SST of the skin tissue ST as the dermatome 100 is moved alongits path of travel PT to excise a section of skin tissue EST. Thus, withthe dermatome 100 of the present disclosure, undertaking a successfulexcising procedure which results in an excised skin tissue section ESThaving a consistent and desired depth or thickness is morestraightforward and less dependent on operator skill level.

FIG. 19 schematically shows the termination of the excising procedure,that is, ending of the cutting of the skin tissue ST in the graftingregion GR with the dermatome 100. Like with the incision, the dermatome100 is manipulated by the operator to have a shallower skin tissuecutting angle STCA of approximately 15°. This shallow skin tissuecutting angle STCA causes the blade 300 to tend to move upwardly throughthe skin tissue SK. If necessary, the operator can slightly wiggle thedermatome 100 in a side-to-side motion to facilitate the rotary knifeblade in cutting upwardly and through the surface of the skin tissue ST.When the blade 300 comes through or emerges from the surface SST of theskin tissue ST, this terminates the cut or excision and determines orfixes the total longitudinal extent LE of the excised skin tissuesection EST.

FIG. 20 schematically depicts the excising of a thicker layer of skintissue ST with the dermatome 100. Here, the dermatome 100 is used forobtaining a full thickness skin graft from a donor graft region GRwherein a depth of a layer DEST of skin tissue EST being excised from adonor graft region GR is on the order of 0.030 in. to 0.043 in.

It should be understood by one of ordinary skill in the art that anapparatus described as the dermatome 100 could be adapted and utilizedfor a wide variety of other medical applications including, but notlimited to, soft tissue harvesting and/or removal, bone harvestingand/or removal, dermatological treatment needs, and other medicalprocedures.

SECOND EXEMPLARY EMBODIMENT Power Operated Dermatome 1000

A second exemplary embodiment of a hand-held, power operated dermatomeof the present disclosure is schematically shown at 1000 in FIGS. 22-24.The power operated dermatome 1000 is similar in configuration andoperation to the power operated dermatome 100, as described above, andthe description of the dermatome 100, as set forth above, is referencedand incorporated herein with respect to the dermatome 1000.

The power operated dermatome includes an elongated handle assembly 1110,similar to the handle assembly 110, and a head assembly 1200, similar tothe head assembly 200, extending from a forward or distal end 1160 ofthe handle assembly 1110. The handle assembly 1110 includes a handle1112 and an actuation lever 1150 and extends between the distal end 1160adjacent the head assembly 1200 and a proximal end 1162. A cover 1170 atthe proximal end 1162 of the handle assembly 1110 is coupled to an airhose 1180 which provides motive power to the drive assembly 1500,similar to the drive assembly 500, of the dermatome 1000. An attachmentassembly 1120, similar to the attachment assembly 120, releasablyaffixes the head assembly 1200 to the handle assembly 1110.

The dermatome 1000 includes the drive assembly 1500, similar to thedrive assembly 500, including a drive motor assembly 1501, similar tothe drive motor assembly 501, and a gear train 1520, similar to the geartrain 520. The gear train 1520, in one exemplary embodiment, comprises apinion gear 1522, similar to the pinion gear 522.

The head assembly 1200 includes a frame body or frame housing 1202,similar to the frame body 202, a rotary knife blade 1300, similar to therotary knife blade 300, a blade housing assembly 1400, including a bladehousing 1410 and a blade lock ring 1450, similar to the blade housingassembly 400, and a depth gauge assembly 1600, similar to the depthgauge assembly 600. The frame body 1202 includes a rearward handleattachment portion 1204 comprising a cylindrical body 1205 and a forwardinterface portion 1206. The frame body 1202 includes a gearbox housing1203 defined by a throughbore 1209 through the frame body 1202. The geartrain 1520 is supported within the gearbox housing 1203. The forwardinterface portion 1206 of the frame body 1202 includes a lower interfaceregion 1210 that extends or transitions between the rearward handleattachment portion 1204 and the annular blade housing 1410 of the bladehousing assembly 1400. The lower interface region 1210 includes agenerally Y-shaped support 1212. The forward interface portion 1206 ofthe frame body 1202 also includes an upper interface region 1220 thatextends or transitions between the rearward handle attachment portion1204 and a central cylindrical support 1602 of the depth gauge assembly1600. The upper interface region 1220 includes a generally V-shaped rib1222 that converges proceeding toward and has a vertex generally at thecentral cylindrical support 1602.

The depth gauge assembly 1600 includes the depth gauge centralcylindrical support 1602, similar to the central cylindrical support602, that extends from the V-shaped rib 1222 of the upper interfaceregion 1220 of the forward interface portion 1206 of the frame body1202. The depth gauge assembly 1600 also includes a depth gauge 1620,similar to the depth gauge 620. The depth gauge 1620 includes the depthgauge shaft 1640 and a depth gauge plate 1622. The depth gauge assembly1600 further includes a depth adjustment knob 1650 and a stop ring 1670,similar to the depth adjustment knob 650 and stop ring 670.

The rotary knife blade 1300 is supported for rotation about an axis ofrotation R′, similar to the axis of rotation R, by the blade housingassembly 1400. The rotary knife blade 1300 includes a cutting edge 1360which defines a cutting plane CP′, similar to the cutting plane CP, andfurther includes a continuous rolling bearing structure 1370, similar tothe continuous rolling bearing structure 370, which defines a rotationalplane RP′ of the blade 1300, similar to the rotational plane RP of theblade 300. The blade housing assembly 1400 includes an annular bladehousing 1410, similar to the blade housing 400, and a blade lock ring450, similar to the blade lock ring 1450, which is releasably affixed tothe blade housing 1410 to trap and secure the rotary knife blade 1300for rotation with respect to the blade housing assembly 1400.

As can best be seen in FIG. 24, the handle assembly 1110 extends along alongitudinal axis LA′ which is canted or angled upwardly at a handleangle HA′ with respect to the cutting plane CP′ and the rotational planeRP′ of the rotary knife blade 1300 and with respect to the planar lowersurface 1624 of the depth gauge plate 1622. That is, a proximal end 1162of the handle assembly 1110 is spaced higher in an upward direction UP′above the cutting plane CP′ of the rotary knife blade 1300 or the planarlower surface 1624 of the depth gauge plate 1622 than is the distal end1160 of the handle assembly 1110. In the dermatome 100, the handle anglewas substantially 0°. In one exemplary embodiment of the dermatome 1000,the handle angle HA′ with respect to the cutting plane CP′ or therotational plane RP′ of the rotary knife blade is in a range of 10°-20°and, more particularly, in one exemplary embodiment, the handle angleHA′ may be approximately 15°. The handle angle HA′ advantageouslyprovides for ease of operation and clearance for the fingers of theoperator. Recall that with the dermatomes 100, 1000 of the presentdisclosure, when excising a layer of skin tissue ST, the operatorgenerally keeps the cutting plane CP′ of the dermatome 1000 flush orflat against the surface SST of the skin tissue ST as the dermatome 1000is moved along its path of travel PT. The upward angle HA′ of the handleassembly 1110 of the dermatome 1000 facilitates keeping the cuttingplane CP′ of the dermatome head assembly 1200 flush or flat against thesurface SST of the skin tissue ST during an excising procedure.

The rearward handle attachment portion 1204 of the frame body 1202 ofthe dermatome 1000 is slightly different than the corresponding rearwardhandle attachment portion 204 of the frame body 202 of the dermatome100. To match the upward canted or tilted handle angle HA′ of the handleassembly 1100, the rearward handle attachment portion 1204 is alsoangled upwardly to match the handle angle of the handle assembly 1100.This can best be seen in FIG. 24. Similarly, the gear train 1520 of thehead assembly 1200 is modified accordingly to account for the differentangle of contact between the pinion gear 1522 and the set of gear teethof the rotary knife blade 1300.

Another difference between the dermatomes 100, 1000 involves an axiallength of the respective depth gauge central cylindrical supports 602,1602. To provide additional laterally stability and accuracy to thedepth gauge plate 1622, in the dermatome 1000, an axial length AL′ wasincreased slightly. Recall that the axial length AL of the cylindricalsupport 602 of the dermatome 100, in one exemplary embodiment, wasapproximately 1.05 in., while the overall axial length of thecylindrical support 602 extending between the upper end 604 of thecylindrical support 602 and the lower end 606 of the cylindrical support602 was approximately 1.25 in. In one exemplary embodiment of thedermatome 100, the axial length AL′ of the cylindrical support isapproximately 1.30 in., while the overall axial length of thecylindrical support 1602 between the upper and lower ends isapproximately 1.50 in.

As used herein, terms of orientation and/or direction such as front,rear, forward, rearward, distal, proximal, distally, proximally, upper,lower, inward, outward, inwardly, outwardly, horizontal, horizontally,vertical, vertically, axial, radial, longitudinal, axially, radially,longitudinally, etc., are provided for convenience purposes and relategenerally to the orientation shown in the Figures and/or discussed inthe Detailed Description. Such orientation/direction terms are notintended to limit the scope of the present disclosure, this application,and/or the invention or inventions described therein, and/or any of theclaims appended hereto. Further, as used herein, the terms comprise,comprises, and comprising are taken to specify the presence of statedfeatures, elements, integers, steps or components, but do not precludethe presence or addition of one or more other features, elements,integers, steps or components.

What have been described above are examples of the present invention. Itis, of course, not possible to describe every conceivable combination ofcomponents or methodologies for purposes of describing the presentinvention, but one of ordinary skill in the art will recognize that manyfurther combinations and permutations of the present invention arepossible. Accordingly, the present invention is intended to embrace allsuch alterations, modifications and variations that fall within thespirit and scope of the appended claims.

What is claimed is:
 1. A head assembly for a power operated dermatome,the head assembly comprising: a frame body supporting a gear train, ablade housing assembly, an annular rotary knife blade supported forrotation about an axis of rotation by the blade housing assembly, therotary knife blade including an inner wall defining an interior regionof the rotary knife blade and having a cutting edge at one end of therotary knife blade defining a cutting plane orthogonal to the axis ofrotation of the rotary knife blade, and a depth gauge assembly includinga depth gauge support and a depth gauge including a depth gauge platesupported by the depth gauge support for axial movement along the axisof rotation of the rotary knife blade, the depth gauge plate extendinginto the interior region of the rotary knife blade and the depth gaugesupport attached to and extending from the frame body.
 2. The headassembly of claim 1 wherein the rotary knife blade includes an annularcontinuous rolling bearing strip which supports the rotary knife bladefor rotation with respect to the blade housing assembly and defines aportion of an outer peripheral surface of the rotary knife blade, therolling bearing strip comprising a plurality of rolling bearingsrotatably supported in spaced apart relation in a flexible separatorcage.
 3. The head assembly of claim 2 wherein the annular continuousrolling bearing strip is seated in a bearing race formed in an outerwall of a body section of the rotary knife blade.
 4. The head assemblyof claim 1 wherein the depth gauge plate includes a planar lower surfaceand an outer peripheral surface, the planar lower surface and the outerperipheral surface defining a lower edge region, an axial distancebetween the lower edge region and the cutting plane of the rotary knifeblade determining a depth of cut of the head assembly.
 5. The headassembly of claim 1 wherein the depth gauge assembly further includes adepth adjustment knob supported by the depth gauge support, rotation ofthe depth adjustment knob changing an axial position of the depth gaugeplate.
 6. The head assembly of claim 1 wherein the depth gauge supportis attached to and extends from an upper interface region of the framebody, the upper interface region comprising a V-shaped rib convergingproceeding toward the depth gauge support.
 7. The head assembly of claim1 wherein the blade housing assembly includes an annular blade housingand a blade lock ring removably attached to the annular blade housing tosecure the rotary knife blade to the blade housing assembly.
 8. The headassembly of claim 7 wherein the annular blade housing is attached to andextends from the frame housing.
 9. The head assembly of claim 7 whereinthe blade housing assembly includes a bearing race that is engaged by acontinuous rolling bearing structure of the rotary knife blade torotatably support the rotary knife blade with respect to the bladehousing assembly, the bearing race of the blade housing assemblycomprising a first bearing surface defined by an inner wall of the bladehousing and a second bearing surface defined by an inner wall by aninner wall of the blade lock ring.
 10. The head assembly of claim 1wherein the gear train is supported in a throughbore of the frame body.11. The head assembly of claim 1 wherein the frame body includesrearward handle attachment portion that is angled upwardly with respectto the cutting plane of the rotary knife blade.
 12. A power operateddermatome comprising: an elongated handle assembly and a head assemblyremovably coupled to the handle assembly, the head assembly including aframe body supporting a gear train, a blade housing assembly, an annularrotary knife blade supported for rotation about an axis of rotation bythe blade housing assembly, the rotary knife blade including an innerwall defining an interior region of the rotary knife blade and having acutting edge at one end of the rotary knife blade defining a cuttingplane orthogonal to the axis of rotation of the rotary knife blade, anda depth gauge assembly including a depth gauge support and a depth gaugeincluding a depth gauge plate supported by the depth gauge for axialmovement along the axis of rotation of the rotary knife blade, the depthgauge plate extending into the interior region of the rotary knife bladeand the depth gauge support attached to and extending from the framebody.
 13. The power operated dermatome of claim 12 wherein the rotaryknife blade includes an annular continuous rolling bearing strip whichsupports the rotary knife blade for rotation with respect to the bladehousing assembly and defines a portion of an outer peripheral surface ofthe rotary knife blade, the rolling bearing strip comprising a pluralityof rolling bearings rotatably supported in spaced apart relation in aflexible separator cage.
 14. The power operated dermatome of claim 13wherein the annular continuous rolling bearing strip is seated in abearing race formed in an outer wall of a body section of the rotaryknife blade.
 15. The power operated dermatome of claim 12 wherein thedepth gauge plate includes a planar lower surface and an outerperipheral surface, the planar lower surface and the outer peripheralsurface defining a lower edge region, an axial distance between thelower edge region and the cutting plane of the rotary knife bladedetermining a depth of cut of the head assembly.
 16. The power operateddermatome of claim 12 wherein the depth gauge assembly further includesa depth adjustment knob supported by the depth gauge support, rotationof the depth adjustment knob changing an axial position of the depthgauge plate.
 17. The power operated dermatome of claim 12 wherein thedepth gauge support is attached to and extends from an upper interfaceregion of the frame body, the upper interface region comprising aV-shaped rib converging proceeding toward the depth gauge support. 18.The power operated dermatome of claim 12 wherein the blade housingassembly includes an annular blade housing and a blade lock ringremovably attached to the annular blade housing to secure the rotaryknife blade to the blade housing assembly.
 19. The power operateddermatome of claim 18 wherein the annular blade housing is attached toand extends from the frame housing.
 20. The power operated dermatome ofclaim 18 wherein the blade housing assembly includes a bearing race thatis engaged by a continuous rolling bearing structure of the rotary knifeblade to rotatably support the rotary knife blade with respect to theblade housing assembly, the bearing race of the blade housing assemblycomprising a first bearing surface defined by an inner wall of the bladehousing and a second bearing surface defined by an inner wall by aninner wall of the blade lock ring.
 21. The power operated dermatome ofclaim 12 wherein the gear train is supported in a throughbore of theframe body.
 22. The power operated dermatome of claim 12 wherein thehandle assembly extends along a longitudinal axis, the handle assemblyoriented with respect to the head assembly such that the longitudinalaxis of the handle assemble is at an upward angle with respect to thecutting plane of the rotary knife blade.
 23. The power operateddermatome of claim 22 wherein the upward angle of the handle assemblywith respect to the cutting plane of the rotary knife blade is in arange of 10 degrees to 20 degrees.
 24. The power operated dermatome ofclaim 22 wherein the upward angle of the handle assembly with respect tothe cutting plane of the rotary knife blade is substantially 15 degrees.25. The power operated dermatome of claim 22 wherein the frame bodyincludes rearward handle attachment portion that is coupled to thehandle assembly, the rearward handle attachment portion being angledupwardly with respect to the cutting plane of the rotary knife blade tomatch the upward angle of the handle assembly.
 26. An apparatus forremoving biological material comprising: a head assembly including aframe body supporting a gear train, a blade housing assembly, an annularrotary knife blade supported for rotation about an axis of rotation bythe blade housing assembly, the rotary knife blade including an innerwall defining an interior region of the rotary knife blade and having acutting edge at one end of the rotary knife blade for engaging thebiological material defining a cutting plane orthogonal to the axis ofrotation of the rotary knife blade, and a depth gauge assembly includinga depth gauge support and a depth gauge including a depth gauge platesupported by the depth gauge support for axial movement along the axisof rotation of the rotary knife blade, the depth gauge plate spacedapart from the cutting plane by an axial distance and extending into theinterior region of the rotary knife blade and the depth gauge supportattached to and extending from the frame body.